Why would any rational American give to a charity this year? The economy is staggering. We lost half a million jobs in November alone. Home foreclosures are at record highs. And while Washington may be wrapping up great piles of economic stimulus and rescue packaging for the holidays (with endless sheets of our best...

Why would any rational American give to a charity this year? The economy is staggering. We lost half a million jobs in November alone. Home foreclosures are at record highs.

And while Washington may be wrapping up great piles of economic stimulus and rescue packaging for the holidays (with endless sheets of our best green paper), the rest of us are winding up a little … short. Grumpy, even.

Meanwhile, charities and social services groups are facing enormous budget shortfalls just as demand for their services is accelerating.

But here’s a surprising paradox. Even in the midst of a financial crisis – just when it seems that everybody should be out for themselves – the single most self-indulgent thing you can do is give.

A bit of time. A little money. Something, anything to a cause you care about.

Here’s why.

A large body of research documents significant and positive health and cognitive benefits directly attributed to giving. And unlike the typical 401(k) lately, these benefits last.

In a joint study by UC Berkeley and Wellesley College, giving in high school was associated with better physical and mental health over five decades, well into late adulthood.

A University of Michigan study of more than 400 older couples – controlling for age, income, gender and physical health – found that those who provide significant support for others (outside their families) were less than half as likely to die in any five-year period.

A 2006 British study on charitable behavior and social status found that 80 percent of groups elect their most generous member – suggesting people believe that an unusually generous person deserves leadership.

So research links charitable giving to better health, longevity, and perhaps even professional success. But if all of that seems too abstract, consider the immediate impact: What’s happening in your brain while you’re writing a check, clicking “send” for a contribution or volunteering a little time to help.

The neurons of people who give generate more dopamine, the “happy” neurotransmitter associated with pleasure, craving and reward.

As Dr. Jorge Moll of the National Institutes of Health has reported, after extensive analysis of MRI brain scans, “anterior sectors of the prefrontal cortex are recruited when altruistic choices prevail over selfish material interests.”

To test this empirically on a live neurologist, I called Dr. Charles Raison of the department of psychiatry and behavioral sciences at the Emory University School of Medicine.

He seemed happy to teach without a tuition check.

“When people do altruistic things,” he explained, “it activates the nucleus accumbens. That’s the pleasure/novelty center of the brain that plays a role in reward, laughter and pleasure.”

Altruism, in other words, is hedonistic.

Why would our brains be wired to give anything away? “Think for a minute about evolution. Altruism is a great way of hedging your bets.”

“We’re hard-wired for it,” he said. “Supporting the tribe is essential for survival. So we evolved to generate a distinct pleasure reaction from helping others. The old impulses are still with us. Generosity is very strongly mediated neurobiologically.”

There is also evidence that the more regularly you give or volunteer, the better you feel. A sort of synaptic remodeling takes place with repeated activity in the brain, an organ that – delightfully contradicting a century’s worth of scientific thought – doesn’t have a set number of neurons. It actually operates on a use-it-or-lose it principle.

To make sense of the season, RedefineChristmas.org mobilizes giving with meaning. At ChangingThePresent.org you can give friends or family a stake in wide range of effective humanitarian and environmental causes. And JustGive.org lets you send them a charity gift card they can use to donate to any of 1.5 million charities, around the world or in their ZIP code.

If you’re not compelled by the piles of humanitarian appeals landing in your mailbox, or just tend to prefer gilt over guilt this season, science is only too glad to tell you that generosity makes you happier – and can literally change your mind.

And with it, other people’s lives. Give something, anything, and you’ll light up the pleasure centers of your brain for the holidays.